Coating of pipes and tubes and like hollow bodies with a bituminous substance in powdered form



Patented Nov. 26, 1929 UNITED STATES PATENT OFFICE ROBERT ILLEMANN AND RALPH ALEXANDER WHITSON, OF GLASGOV, SCOTLAND COATING OF PIPES AND TUBES AND LIKE HOLLO'W' BODIES WITH A BITUMINOUS SUBSTANCE IN POWDERED FORM No Drawing. Application filed December 22, 1927, Serial No. 242,006, and in Great Britain January 26, 1927.

This invention relates to an improved process for coating concrete and metal pipes, tubes and like hollow bodies with asphalt powder in a hot state.

The invention consists in a process for coating concrete and metal pipes, tubes and like hollow bodies with asphalt powder, in which, first, bitumen or a bituminous composition is applied in the form of a film to the surface of the pipe or the like to be coated and, then, a coating of hot asphalt powder is applied on top of the bituminous film and, thereafter, the said coating of asphalt powder is pressed and smoothed, and, finally cooled or allowed to cool.

A coating thus prepared is applicable to either the outside or inside surfaces of pipes or the like, and the asphalt powder employed may consist either of powdered natural rock asphalt (that is, limestone naturally impregnated with bitumen) or may consist of pow- :lered asphalt made artificially. For pressing the asphalt powder upon the surface of the pipe or the like, any suitable means such as pneumatic rammers may be used and (or) centrifugal force may be utilized.

In lining the interior surface of a hollow body such as a concrete pipe, we may apply the adhesive film of bitumen or bituminous composition to the surface in any known manner, as, for example, by dipping, spraying, painting or by centrifugal force, and, thereafter, we may apply the hoLa sphalt pgwdeggn top of the said adhesive film centrifugally,orbyother suitable means. Ineach case, manual or power operated means are subsequently used to press and smooth the complete lining.

One method of lining a pipe, in which the bituminous film and asphalt powder are both applied centrifugally, is as follows The pipe is placed in a horizontal position and rapidly spun round its own aXis. A long trough, capable of being tilted to either side,

is then filled with hot liquid bitumen or bituminous composition and, while the pipe is spinning, the trough is projected into the interior thereof and, when completely inserted, it is tilted to one side so that the bitumen or bituminous composition is discharged and distributed evenly over the interior surface of the pipe by centrifugal force. Thereafter the trough is righted and withdrawn from the interior of the pipe. Hot asphalt powder is then introduced into the trough which is thereupon inserted once more into the pipe and tilted over gradually so that the powder can be distributed evenly over the adhesive film of bitumen or bituminous composition by centrifugal action. In order that the lining of asphalt powder may be pressed and (or) smoothed, the trough is or may be fitted with a ramming or smoothing device capable of being brought to bear on the lining by movement of the trough transversely of the pipe. Preferably, the pressure of the ramn'iing or smoothing device is variable, and to ensure that the said pressure is applied normal to the lining, the device may com prise a roller or the like. If desired, a separate trough may be used for the introduction of the asphalt'powder.

It will be understood that the bituminous film acts as a key between the surface of the pipe or the like and the asphalt powder and enables a coating of asphalt powder to be applied more effectively, particularly by centrifugal means, than hitherto. The asphalt powder generally consists mainly of limestone, silica or similar mineral matters containing from 9% to 25% bitumen and, while being heated, it is agitated by mechanical or other stirrers. The powder is preferably heated to a temperature of from 90 F. to 180 F. according to the melting point of the bitumen which the powder may contain. In lining the interior of metal pipes and like bodies, the body itself is preferably heated before the application of the bituminous film and asphalt powder.

By means of the process described a coating is produced which adheres tenaciously to the surface of the pipe or the like and which does not creep or flow in hot climates. In our process, furthermore, asphalt powders having a low percentage of bitumen may be successfully used.

We claim v 1. Hollow bodies having a coating which comprises a coat of adhesive bituminous sub stance spread over the surface of the body, and an outer coat of asphalt powder consolidated on said adhesive coat.

2. Hollow bodies having a coating which 5 comprises a coat of adhesive bituminous substance spread over the surface of the body, and an outer coat of powdered natural rock asphalt consolidated on said adhesive coat. 3. In the manufacture of bituminously coated hollow bodies, the steps of heating asphalt powder, superimposing on the bituminous oo'ating of the body a coat of said heated asphalt powder, and consolidating said asphalt powder on said bituminous coating by pressure so as to provide a coating which does not creep or flow in hot climates. 4. In the manufacture of bituminously lined hollow bodies such as pipes and the like, the steps of heating asphalt powder, distributing a coat of said heated asphalt powder over the bituminous coating of the body by centritugalaction, and consolidating said asphalt powder on said bituminous coating by pressure so as to provide a coating which does not creep 0r flow in hot climates.

In testimony whereof we aflix our signatures.

ROBERT ILLEMANN. RALPH ALEXANDER \VHITSON. 

